Understand that the W-4 goes to your employer only. The IRS never sees it. Ever. They employer uses that form to determine how much tax to withhold from your paychecks. If W-2 income is your ONLY SOURCE of income, then both of you can claim a maximum of 3 exemplions. One for yourself, one for your spouse, and one for your dependent child that lives with both of you, assuming you both live under the same roof.
If you claim less exemptions, that just means the employer withholds more from your paychecks. Then when you file your joint return claiming your self-exemptions plus your dependent child, you are practically guaranteed a refund.
